Wanted electronize 4qd DMR203

[John Fitzsimons]

Hi all, just wondering if anyone has a spare electronize DMR-203 available. I was bench testing pack that came with one of my tigers. Works occasionally then not. Pulled unit from other tiger and seems to point to the DMR 203 as the problem.

Regards
John

[Richard Goodwin]

Hi John,

Have stripped out the 4QD drivers and the DM203 from Tiger #312 in prep for upgrading to sabretooth drivers. I will be selling as a system soon if interested?
Richard

[Mark Heaps]

Have you checked if the symptoms re-occur when you plug the suspect module back in ? Or if they occur in the known working tank if you put the suspect module in it ?
If not then the module has not yet been proven to be at fault.
I see from the photo that the plugs are crimp-type connectors and I absolutely hate them.
I once took over from a guy known by the nickname "Scotch-lock Pete" as he would them to repair a cable fault rather than doing a proper solder repair. For my 3 years at that unit, I diagnosed 95% of the faults on the vehicles down to failed Scotch-lock that he had used as a repair.
Fine to use as a temporary get-you-home repair but not to be considered as a long-term fix.

[John Fitzsimons]

Hi Mark,
I am sure it is the unit. I was bench testing the kit. It had been in a box unused since I picked up the vehicle. When I encountered the problem I switched out the dmr 203 to my other working tiger using that tigers connectors and same problem again.
Basically no signal from transmitter through the interface. If I adjust the trim switch on the radio off center I get movement then can re-center sticks and motors respond well. When I switch off and back on again, back to square one. Interface can send a signal but something not right.

I took the DMR 203 from my skkfz 222 motion kit and that works well.

I am now wondering if the Tiger 1 DMR203 and Sdkfz 222 DMR203 were mixed up at some stage and would that make any difference. I will test the unit in the Sdkfz 222 motion kit to see if it works with that?

[John Fitzsimons]

Hi John,

Have stripped out the 4QD drivers and the DM203 from Tiger #312 in prep for upgrading to sabretooth drivers. I will be selling as a system soon if interested?
Richard

Thanks Richard,

I am hoping to replace just the DMR203 if possible. I will be interested to see how you get on with the sabretooth drivers. Are you keeping the 4qd motors?

Great to see another 312. I hope to get mine out soon for some photos and video. Almost ready to run.

[Adrian Harris]

There are jumpers inside the DMR203 but I don't think they would affect how it works.

I know the DMR203 will only work if there's a signal on Inp1, so you can't run it with just Inp2.

If you don't have the manual I could email it to you.

Adrian.

NB: It's Sabertooth not Sabretooth, in case Google can't find them.

[Steve Stuart]

The Jumpers do make a difference, they can be used to produce one stick driving. This is what I did for my Cromwell! If Adrian sends you the manual, hopefully all will be revealed.
Steve

[John Fitzsimons]

There are jumpers inside the DMR203 but I don't think they would affect how it works.

I know the DMR203 will only work if there's a signal on Inp1, so you can't run it with just Inp2.

If you don't have the manual I could email it to you.

Adrian.

NB: It's Sabertooth not Sabretooth, in case Google can't find them.

Thanks Adrian, I would be interested in manual if you have one.
It's a bit odd how messing with the trim makes it work perfectly for a while then not working when you switch off and back on.

[Sam Hough]

The manual is still online (good for 4qd!) https://www.4qd.co.uk/wp-content/upload ... DMR203.pdf

I have a spare one too if you get really stuck. I was holding on to it if I ever see sense and give up on totally custom tx/rx.

I reverse engineered it a bit to still drive the 4qd power controls but from a raspberry pi. There is very little to go wrong in there so it is odd.

Good luck, these things are very annoying when the glitch.

Cheers

Sam

[Sam Hough]

I've just remembered that I had very odd (and hard to track down) problems when I had a poor connection between the power units and the motors. I was having trouble setting neutral although the bigger problem was the drives direction getting stuck.

I was assuming the relay clicking was a good way to test the trim but that turned out to be wrong. It does say in the VTX manual;

"Do Not: Try to test the controller with no motor
connected. You won't harm the controller but
reversing will not operate properly."

Cheers

Sam

[Richard Goodwin]

John,

Yes am keeping the motors, just changing out the drivers.

Richard

[John Fitzsimons]

I've just remembered that I had very odd (and hard to track down) problems when I had a poor connection between the power units and the motors. I was having trouble setting neutral although the bigger problem was the drives direction getting stuck.

I was assuming the relay clicking was a good way to test the trim but that turned out to be wrong. It does say in the VTX manual;

"Do Not: Try to test the controller with no motor
connected. You won't harm the controller but
reversing will not operate properly."

Cheers

Sam

Thanks Sam. I had the motors connected.

John

[Mark Heaps]

Hi Mark,
I am sure it is the unit. I was bench testing the kit. It had been in a box unused since I picked up the vehicle. When I encountered the problem I switched out the dmr 203 to my other working tiger using that tigers connectors and same problem again.

Hi John,
With that info ( which was not in your original post ), I would agree that the unit is faulty.
You have done the double check which is step one, good unit in - symptoms gone - fault localised - suspect unit identified. Step two either suspect unit back in - symptoms re-occur or much better put suspect unit in known working system - symptoms appear there. Suspect unit confirmed defective.
A lot of electrical faults are caused by resistance build-up on the connectors ( tarnishing on the contact surfaces ). Unplugging the unit and plugging in a new one cleans the surfaces and will rectify the fault if that was the problem. Unplugging and replugging the suspect unit would also rectify the fault if that was the problem.
The double check confirms what the problem is and can save unneccessary expense caused by purchasing a replacement item when it is not required.

[John Fitzsimons]

Thanks Mark, I will try cleaning all the connectors. Could be the problem. I need to bench test the sdkfz 222 electrics anyway. These packs have been in my workshop for a few years now.